Composite separation membrane

Inactive Publication Date: 2011-01-27
9 Cites 7 Cited by

AI-Extracted Technical Summary

Problems solved by technology

However, this membrane has problems with hydrolysis resistance, microbial resistance, etc., and is also insufficient in salt removal rate and water permeability.
Therefore, the cellulose acetate asymmetric membrane has not been put to practical use yet in a wide range of applications, while the membrane has been used for some applications.
However, such a composite separation membrane using a polyamide includes an amide linkage in its main chain, and thus still has insufficient chemical resistance, and it is known that the desalination performance and selective separation performance are significantly degraded due to a treatment with chlorine,...
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Method used

[0013]In the polyhedral silsesquioxane for use in the present invention, the moiety represented by R1 represents a reactive moiety which is polymerizable with the hydrophilic monomer. The polyhedral silsesquioxane bonded to the hydrophilic monomer with two or more (n≧2) reactive moieties interposed therebetween form a cross-linked structure, thereby resulting in improvement of the resistance to dissolution in a variety of solvents, in particular, water. In the case of a separation membrane obtained by polymerizing a hydrophilic monomer singly with a polyhedral silsesquioxane including no reactive moiety, the structure of the separation membrane is changed by swelling depending on the hydrophilicity of the hydrophilic monomer, or by elution, and there is thus concern that the membrane separation performance will be degraded. Therefore, the separation membrane composed of the polymer of the polyhedral silsesquioxane and hydrophilic monomer come to have extremely high water permeability performance with a combination of voids at the molecular level, which derives from the three-dimensionally steric structure of the polyhedral silsesquioxane, and the improvement in hydrophilicity with the hydrophilic monomer.
[0019]The hydrophilic monomer for use in the present invention needs to be a hydrophilic monomer including a reactive moiety which is able to be bonded to the polymerizable reactive moiety of the polyhedral silsesquioxane. In addition, the hydrophilic monomer needs to be a monomer containing a hetero atom in order to increase the selective water permeability when the composite separation membrane is used for separation of a solution or the like. This hydrophilic monomer may be a compound of a straight-chain monomer containing a hetero atom or a compound which has a hetero ring structure. These hydrophilic monomers may be used singly, or multiple types of the hydrophilic monomers can be used in combination.
[0026]In addition, it is preferable to add a polymerization initiator, a polymerization promoter, etc., in the formation of the separation function layer for the purposed of increasing the polymerization rate. The polymerization initiator and the polymerization promoter herein are not particularly limited, and appropriately selected depending on the structures of the polyhedral...
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Benefits of technology

[0010]According to the present invention, a composite separation membrane can be provided which has excellent chemical resistance and water permeabil...
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In order to obtain a composite separation membrane which has excellent chemical resistance, separation performance and water permeability at the same time, the present invention provides a composite separation membrane comprising a separation function layer on a porous supporting membrane, characterized in that the separation function layer contains at least a polymer of a polyhedral silsesquioxane represented by the following general formula (a) and a hydrophilic monomer.
(R1SiO1.5)n(R2SiO1.5)m  General Formula (a)
(In the formula, R1 includes a polymerizable reactive moiety; R2 represents a hydrogen atom or an alkyl group, which may be substituted; and n and m each represent an integer satisfying n≧2 or m≧0, with n+m being 8, 10 or 12.)

Application Domain

Semi-permeable membranesMembranes +1

Technology Topic

ChemistryHydrophilic monomer +3


  • Experimental program(5)


Reference Example 1
[0047]The porous supporting membrane reinforced with a fiber, used in the present invention, was produced in accordance with the following approach.
[0048]Taffeta (150-denier multifilament yarn for both warp yarn and weft yarn, weaving density: 90 yarns/inch in the length direction and 67 yarns/inch, thickness: 160 μm) composed of a 30 cm long×20 cm wide polyester fiber was fixed to a glass plate, and a 15 weight % dimethylformamide solution of polysulfone (Udel (Registered Trademark) produced by Amoco, P-3500) was casted thereon at room temperature (25° C.) to provide a thickness of 200 μm, immediately followed by immersion in pure water and leaving as it was for 5 minutes, thereby obtaining a porous supporting membrane. The pure water permeation coefficient of the thus obtained porous supporting membrane was 0.005 to 0.01 kg/cm2/sec/atm (about 0.001 to 0.002 g/cm2/sec/MPa), which was measured at a pressure of 0.1 MPa and a temperature of 25° C. In addition, the average pore size at the surface of the obtained porous supporting membrane was 20 to 50 nm, and the thickness of the polysulfone moiety thereof was 50 μm.


Example 1
[0049]The porous supporting membrane produced in accordance with Reference Example 1 was brought into contact with an isopropyl alcohol solution containing 3.6 weight % of sodium styrenesulfonate, 0.4 weight % of Methacryl-POSS (polyhedral oligomeric silsesquioxane), 0.24 weight % of 2,2-dimethoxy-2-phenylacetophenone as an α-hydroxyacetophenone type photopolymerization initiator, and 33.5 weight % of pure water for 1 minute, and nitrogen was sprayed from an air nozzle to remove the extra solution from the surface of the porous supporting membrane, thereby forming a layer of the solution on the porous supporting membrane. Then, with the use of an excimer lamp (UER 20-172) produced by Ushio, inc., capable of irradiation with ultraviolet rays of 172 nm, the distance between the excimer lamp and the porous supporting membrane was set to 1 cm under a nitrogen atmosphere with an oxygen concentration of 0.1% or less, and irradiation with ultraviolet rays was carried out for 5 minutes to produce a composite separation membrane with a polymer of a polyhedral silsesquioxane and a hydrophilic monomer formed on the surface of the porous supporting membrane. Then, immersion in a 10 weight % isopropyl alcohol solution for 10 minutes was carried out for development of hydrophilicity. The thickness of the thus obtained polymer was 250 nm on average according to confirmation by UHR-FE-SEM. In addition, the thus obtained composite separation membrane was subj acted to a reverse osmosis test under the conditions of 0.5 MPa and 25° C., with the use of, as raw water, a 500 ppm salt solution adjusted to pH 6.5 with hydrochloric acid or sodium hydroxide, thereby obtaining the performance shown in Table 1 as the result of the test. In addition, the thickness of the thus obtained polymer was 250 nm on average according to confirmation by UHR-FE-SEM.


Example 2
[0050]A composite separation membrane was produced in the same way as in Example 1, except that an isopropyl alcohol solution containing 1.8 weight % of an acrylic acid, 0.2 weight % of Methacryl-POSS, and 0.12 weight % of 2,2-dimethoxy-2-phenyl acetophenone was used instead of the solution applied onto the porous supporting membrane in Example 1. The thus obtained composite separation membrane was evaluated in the same way as in Example 1 to obtain the performance shown in Table 1.


Pore size0.001 ~ 0.1μm

Description & Claims & Application Information

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